Cross-coupled YBCO BPFs with Wide Upper Stopband Using Quarter-wavelength Stepped-impedance Resonators

Chung-I G. Hsu；Li-Ming Wang；Li-Shian Chen；Ching-Her Lee

Chinese Journal of Physics

45卷2s2期（2007 / 04 / 01）

273 - 280

繁體中文

This paper presents a cross-coupled high-temperature superconducting (HTS) bandpass filter (BPF) design using quarter-wavelength stepped-impedance resonators (λ/4SIRs) for the wireless communication applications. A pair of transmission zeros associated with the cross-coupled configuration is designed to be placed near the passband skirts, greatly sharpening the rolling-off at the passband edges. The spurious-passband center frequency of the BPF using λ/4 SIRs is simulated to be higher than that of the BPF adoptingλ/2 SIRs. ABPF usingλ/4 SIRs, conceived to be smaller than the corresponding BPF usingλ/2 SIRs, has been fabricated by double-sided depositing patterned YBCO film on a 10-mm-square and 0.5-mm-thick LaAlO3 substrate and by putting them in a copper housing. The measured results revealed that this BPF has a very wide stopband bandwidth beyond the desired passband.